Yeast removal from vessels by fluidity increase



United States Patent 3,415,657 YEAST REMOVAL FROM VESSELS BY FLUIDITY INCREASE Cavit Akin, St. Louis, Mo., assignor to Falstaff Brewing Corporation, St. Louis, Mo., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 473,211, July 19, 1965. This application Aug. 3, 1967, Ser. No. 658,063

Claims. (CI. 99-96) ABSTRACT OF THE DISCLOSURE Removal of yeast from a vessel or fermenter by increasing the fluidity of the yeast slurry with a solution of a suitable acid or base character such that the viscosity of the slurry is conditioned to allow easy flow, and for this purpose phosphoric acid accomplishes the desired result and also helps disinfection and nutrition of the yeast.

This application is a continuation-in-part of my prior application, Ser. No. 473,211, filed July 19, 1965 now abandoned.

This invention relates to yeast removal, and more particularly to yeast removal from fermenters by altering the viscosity of yeast slurry remaining in a fermenter after the fermentation product, such as beer, has been removed.

Heretofore yeast removal from fermenters, after fermentation products, such as beer, have been withdrawn, was a time consuming and expensive task particularly when the yeast slurry was to be recovered and reused. After beer fermentation, the remaining yeast settles to the bottom of the fermenter tank and forms a pseudoplastic mass. This yeast mass remains attached to the bottom of the fermenter even in pitched bottom fermenters and moves to the lowest end very slowly. Most prior processes for removing yeast slurry from 'fermenters included excessive dilution of the yeast slurry or manual scraping of the fermenter tank. Some fermenters are equipped with spray nozzles to dilute and wash the yeast slurry from the fermenter. Hence, additional handling and settling of the yeast was required.

The present invention overcomes the difficulties of prior techniques and eliminates the necessity for such time con suming and expensive processes. Briefly, the invention contemplates reducing the consistency of the yeast slurry without excessive dilution by adding a sufficient quantity of 1 to 10 normal alkali or acid solution to yeast slurry based on the yeast slurry having 14 to 17 percent total solids to provide 1 to 10 equivalent weights of alkali or acid per 100 pounds of yeast slurry. Hence, with relatively nominal solution additions, the increase in fluidity is substantial. The fluidity change is attributable mainly to the degree of hydrolysis which occurs from acid or alkali additions to the yeast slurry rather than the change in pH.

It is therefore an important object of the invention to provide a process for yeast removal from ferment ers which is economical and simple, yet highly effective.

It is another object of the invention to provide a method of removing yeast slurry from a fermentation tank by reducing the consistency of the yeast slurry without excessive dilution.

It is still another object of the invention to provide a method of removing yeast slurry from fermentation tanks by adding nominal amounts of acid or alkaline control solutions to increase fluidity of the yeast slurry without significant dilution thereof, and draining the yeast slurry from the fermentation tanks.

It is still another object of the invention to provide a method of removing yeast slurry from fermentation 3,415,657 Patented Dec. 10, 1968 tanks by spraying acid or alkaline control solution in nominal amounts onto the yeast slurry in the bottom of a fermentation vessel to increase the fluidity of the yeast slurry sufiicient to permit drainage from the fermentation vessel.

It is still another object of the invention to provide a method of removing yeast slurry from fermentation vessels which includes reducing the consistency of the yeast slurry by adding nominal amounts of a basic solution to the yeast slurry and thereafter draining the yeast slurry from the fermentation vessels.

It is still another object of the invention to provide a method of removing yeast slurry from fermentation vessels which includes increasing the fluidity of the yeast slurry with nominal additions of an acidic solution to the yeast slurry and thereafter draining the yeast slurry from the fermentation tanks.

Other objects and advantages of the invention will be readily appreciated from the ensuing detailed description of the invention in conjunction with the appended claims.

In accordance with the usual fermentation process, When the fermentation process is completed and the yeast settles to the bottom of the fermentation vessel, the fermentation product or beer is withdrawn from the fermentation vessel and the yeast slurry remains attached to the bottom of the fermentation vessel as a pseudoplastic mass. In accordance with the present invention, the pseudo-plastic mass or yeast slurry is treated preferably with about one (1) to ten (10) equivalent weight alkali per pounds of yeast slurry at 14 to 17 percent solids. The equivalent weight is added in solution from a 1 to 10 normal alkali solution. The alkali solution preferably is sodium hydroxide; however, it maybe any suitable alkaline solution. Moreover, the consistency control solution may be an acid. About one 1) to ten l0) equivalent weights acid per 100 pounds of yeast slurry at 14 to 17 percent solids may be used to achieve consistency control. The equivalent weight is added in solution from a one (1) to ten (10) normal acid solution. Any suitable acid such as hydrochloric acid may be used. The slurry usually has a pH of 4 to 5 and when treated with acid a pH of 3 or less; when treated with alkaline solution a pH of 6 to 8. However, the final pH is not as significant as the degree of hydrolysis of inter-cell material accomplished from the acid or alkaline additions.

Although hydrochloric acid or any suitable acid can be used, the use of phosphoric acid may be preferred in certain cases due to its widespread acceptance in food processing. Phosphoric acid is commonly applied to disinfect the yeast; also the phosphate ions of the phosphoric acid is utilized by yeast as a nutrient. Thus, the application of phosphoric acid for the automatic removal of yeast also helps disinfection and nutrition of the yeast. Phosphoric acid should be added at a rate of about one 1) to ten (10) equivalent weights in form of a water or beer solution per 100 pounds of yeast.

The process of yeast slurry removal may be accomplished by dispersing the control alkaline or acid solution over the surface of the yeast slurry without the necessity of mixing the yeast slurry. In fermentation vessels equipped with spray rinses, the control solution may be introduced through such spray apparatus. Likewise, portable spray apparatus may be used to disperse the control solution. Once the consistency control solution has been added, the yeast slurry may be readily withdrawn from the fermentation vessel quickly and completely. After the yeast slurry has been withdrawn the pH may be readjusted to between a pH of 4 to 5. Thus, hydrolysis of the yeast slurry is prevented, although the consistency of the yeast slurry does not return to the initial consistency that it had in the fermentation vessel prior to treatment.

3,415,657 3 4 The specific examples hereinafter set forth fully illustrate Example IV the effectiveness of the process.

In the proceeding Examples I, II and III the yeast Example I slurry was mixed with the acidic or alkali solution and Samples of yeast slurry from a fermentation vessel with the consistency was determined right away. However, it

a pH between 4 to 5 and total solids of 14 to 17 percent is known that the plastic charatcer of yeast changes as it were used with various one (1) ml. additions of water and is stirred. In this example, the yeast slurry was allowed acid solutions to determine the change in consistency of the a rest time of 20 minutes at 3 C. in the Bostwick Conyeast slurry. The yeast slurries were mixed and without sistometer prior to dispersing 1 ml. of 4 N Sodium Hydelay, for purposes of comparison, Bostwick consistometer droxide solution on the surface of each sample of the yeast readings of distance travelled per unit of time were deter- 1O slurry. The consistency was determined at 3 C. after mined. The samples with results are tabulated in Table I contact times of /2 to 5 minutes. The samples and results below. are tabulated in Table IV below.

TABLE I Consistometer Results Sample No. Wt. (gm) 1 ml. Slurry pII CM Travelled per minute Additions 30. 9 IN HCl 2.10 is 21 2 5 23.5 28.9 2N HC1.. 1.80 16 18 20 20 30.4 3N HCl. 1.08 17 1s 19 28.7 Water 4.2 6. 5 7 5 a5 9 1 Control addition.

It will be observed from Table I that the fluidity of TABLE IV yeast slurry w1th ac1d addition increased markedly over 20 the water addition control sam 1e with ver nomina ilu- Consiswmeter p y I d Contact Tune Results CM Travelled ilOIl. Sample No. Wt. (gm.) afteigdispersing per minute am 1 I itive Ex p e I 1 1% 2 Samples of yeast slurry as used in Example I were 65.72 Zminutes. 17 20% 22 23y prepared w1th various one (1) ml. additions of water and 67.10 lminuteh 1a% 15% 17 191/; basic solutions. The yeast slurry was 14% solid based on 5333 18 g oven dried sample weight. Again the Bostwick Consis- 63.50 5minutes 13% 15 16 17 tometer was used to determine changes in consistency of the yeast slurries immediately after mixing. The samples The data in Table IV indicates that 2 minutes contact w1th results are tabulated 1n Table II below. time was the best, however, all the times were adequate TABLE II 30.2 4. 02 5y 6 7 7% 37.6 4. 35 6% 7% 8 s 35.5 4.54 6% 7% s 8% 39.5 4.5 7 8 8% 9 37.9 4.52 5% 6% 7 7% 37.5 4.75 6 7 7% s 37.7 4.70 6% 7% s 8% 38.6 4.98 6 7% s 8% 36.9 5.63 7 8% 9 10 37.5 6.5 9 10% 11 11% It will be observed from Table II that Sample 14 underto permit quick removal of yeast slurry of such consiswent a significant increase in fluidity. tency from a fermentation vessel.

Example III Example V Example II was repeated using 1 to 5 N sodium hy- This example illustrates that additions of alkali to yeast droxide along w1th a water addition control sample. The slurry and readjusting the pH to the initial value of the samples and results obtained with the Bostwick Consisyeast slurry does not aifect the fermentation. In this extometer are tabulated in Table III below. ample 1 ml. of 1 N sodium hydroxide was added to about TABLE III Consistometer Results CM Travelled per minute Sample No. Wt. (gm) 1 m1.

Additions Final pH Generally, it will be noted from Table III that as the 30 grams of yeast slurry (approximately 15% solids) and normality of NaOH solution increased fluidity of the yeast kept in contact for four hours. Then, the pH was adjusted slurries increased markedly. The best fluidity value was to about 4 by addition of 1 N HCl. A sample of 8 grams obtained with 4 N NaOH. of the readjusted pH yeast slurry was added to a 1000 ml.

6 sample of wort. A control sample of 8 grams of untreated not limited to any particular apparatus for making addiyeast slurry was added to a 1000 ml. sample of wort. tions of such acids and alkalies. Both samples were allowed to ferment. The fermentation Various modifications and changes will be apparent time and results are tabulated in Table V below. from the foregoing, and all such modifications and TABLE V Time, hours 0 17 22 24 29 44 49 65 70 Test Sample, Percent Total Solids 11.5 9.6 8.5 7.1 6.5 Control Sample. Percent Total Solids 11.5 8.5 8.0 7.4 6.5

From the data in Table V, it will be noted that the ferchanges are deemed to be within the scope of the inveninentation was relatively unaffected by alkali additions tion as defined in the appended claims. and readjustment of pH. The test sample started slower, What is claimed is: but finished faster than the control sample. 1. A method of removing yeast slurry from a vessel Example VI comprising the steps of increasing the fluidity of the yeast slurry in said vessel by changing the pH thereof with the addition of a suflicient quantity of an acid solution to bring the pH downward to less than about 3 and thereafter removing the fluidized yeast from the vessel.

2. The method set forth in claim 1 wherein the quan- Samples of yeast slurry from a fermentation vessel with a pH between 4 to 5 and total solids of 14 to 17 percent were used for various one ml. additions of water and phosphoric acid at different concentrations to determine the change in consistency of the yeast slurry. The

yeast l i were mixed and Without delay, for purpose tity of said acid solution contains one equivalent weight of comparison, Bostwick consistometer readings of dis- 0f the acld for between 10 t0 Pounds of the Yeast tance travelled per unit time were determined. The samples Slurry based on said Slurry having 14 17% total Solids- With results are tabulated in Table VI. 3. The method set forth in claim 1 wherein the con- TABLE VI.BOSTWIOK CONSISIOMETER MEASUREMENTS WITH YEAST SLURRY-PHOSPHORIC ACID MIXTURES (3 C.)

l Distilled water.

It will be observed from Table VI that the fluidity of centration of the acid to be added is about 1 normal to 10 yeast slurry with phosphoric acid addition increased normal. markedly over the water addition control sample with 4. The method set forth in claim 1 wherein the acid very nominal dilution. solution is hydrochloric.

5. The method set forth in claim 1 wherein the acid Examp 16 VII solution is phosphoric.

This example illustrates the increase in fluidity achieved 6. A method of removing yeast slurry from a vessel by the invention. Two samples of yeast slurry of 1000 ml. comprising the steps of increasing the fluidity of the yeast each were placed on trays to form one inch deep layers. slurry in said vessel by changing the pH thereof with the The trays were tilted at an angle of about 2.4". The samaddition of a sufficient quantity of an alkali solution to ples were maintained at 3 C. for 4 hours and the test was bring the pH upward to more than about 6 and thereperformed at 3 C. One sample surface was sprayed with after removing the fluidized yeast from the vessel.

10 ml. of 5 N sodium hydroxide solution from an atomizer 7. The method set forth in 6 wherein the quantity of and the yeast slurry was removed by suction at the lowersaid alkali solution contains one equivalent weight of most end of the tray. By using intermittent sprays, 90% 50 the alkali for between 10 to 100 pounds of the yeast of the yeast slurry was removed within 10 minutes. The slurry based on said slurry having 14 to 17% total solids.

other sample surface was squirted with 5 ml. of 5 N 8. The method set forth in claim 6 wherein the consodium hydroxide solution from a wash bottle. This arcentration of the alkali to be added is about 1 normal to rangement provided a pressure impact. Although the entire 10 normal.

surface of the yeast did not have direct contact with the 9. The method set forth in claim 6 wherein the alkali sodium hydroxide solution, large areas of the sample solution is potassium hydroxide.

flowed. When stirred, the entire sample became fluid. 10. The method set forth in claim 6 wherein the alkali It will therefore be understood that the method of re- Sol ion is Sodium hydroxide.

ducing the consistency of yeast slurry may be readily accomplished in fermentation vessels equipped with spray References Cited apparatus by intermi ttently spraying the yeast slurry with UNITED STATES PATENTS 1 to 3 N acid solution or 1 to 5 N alkali solution. Of

course portable spray equipment may be used. Also the 2,609,328 9/1952 Reed 195*74 X desired fluidity can be accomplished by mixing the acid or 3,117,005 1/1964 Coutts X alkali solution in the fermentation vessel. Once the yeast 3186 922 6/1965 Champagnat 99*96 X slurry has been removed from the fermentation vessel, it may be readjusted to the previous pH concentration to LIONEL SHAPIROPrmary Examine"- eliminate Yfiast y y D. M. NAFF, Assistant Examiner.

It will be understood that the foregoing is illustrative of the invention, and the acids and alkalies used are not US. Cl. X.R.

limited to HCl or NaOH, and as well, the invention is -82, 74 

